Slack adjuster



July 13, 1965 KE J. BRANDT 3,194,358

l sLAck ADJUSTER Filed Jan. 9, 1964 2 Sheets-Sheet 1 INVENTOR.

L M BY m, Mw/K 1Km July 13, 1965 KE J. BRANDT 3,194,358

SLACK ADJ US TER INVENTOR.

United States Patent O 3,194,358 SLACK ADJUSTER Ake J. Brandt, ParkForest, Ill., assigner to American SAB Company, Ine., Chicago, lli.Filed `lan. 9, 1964, Ser. No. 336,666 4 laims. (Si. 1881%) Thisinvention relates to an lautomatic slack adjuster for brakes, especiallyfor use in the brake rigging of railway cars.

Moreparticularly, the invention relates to a doubleacting slackadjuster, i.e., a device by means of which a -too great slack in therigging, e.g., resulting from wear, may be reduced and a .too smallslack, eg., resulting from the replacement of brakes shoes, may beincreased.

Still more particularly, the invention relates to a slack adjuster ofthe pure-ly mechanical type comprising two interconnected brake rodpar-ts which may be axially displaced relative to one another by meansof :a screw and nut connection.

It is the object of the invention to devise a slack adjuster of the typereferred to which is cheap in manufacture and reliable in oper-ation,which comprises a minimum number of moving parts and no exposed rotatingparts, which is rap-id in action both when taking up slack and whenpaying out, and which offers only a relatively low resistance to thetransmission of the braking force.

It is a further object of the invention to devise a slack adjuster ofthe type referred to which is cheap in manuof which will allow anydesired amount of taking up and paying out slack.

From one point of view, the slack adjuster according to the inventionmay be characterized principally by the manner in which the variouselements of which it is composed are `arranged to engage with oneanother, either directly or indirectly, in the axial direction of theslack adjuster. rFor the purpose of such characterization, the followingexpressions will be used:

The forward direction is defined as the direction of movement, duringapplication of the br-akes, of the brake rod in which the slackyadjuster is mounted. The expressions front and rear refer to therelative location of parts as viewed in the same direction. An elementis said to be forwardly engageable with another element when the faceexerted by the former element on the latter element is in the forwarddirection. The engagement may be either direct or indirect, i.e.,through 4intervening elements. Similarly, an element is said to berearwardly engageable wi-th another element when the force exerted bythe former element on the latter element is in the rearward direction.An element is said to be rotationally engageable with another element,when the engagement is of a character permitting substantiallyunrestrained mutual rotation of the two elements, e.g., through theintermediary of a -ball bearing. Similarly, an element is said to beclutchably engageable with another elemen't when the engagement is of acharacter offering substantial resistance to mutual rotation of the twoelements. Examples of clutchable engagement are frictional engagementand -toothed engagement. The line of distinction between rotational andclutchable engagement is whethertheengagement is of a character topermit or prevent rotation of .the nuts referred to below under theinfluence of axialforces.

As characterized fro-m this point of View, an automatic slack adjusteraccording to the invention comprises an elongated housing, a front rod.part extending into said housing from the front end thereof, a rear rodpart extending into said housing from the rear end thereof, and beingVconstructed with a steep screw thread, a locking 3,l4,358 Patented July13, 1965 "ice nut and a feeding nut on said screw thread, said lockingnut being forwardly rotationally engageable and rearwardly clutchablyengageable with said front rod part, said feeding nut being forwardlyclutchably engageable with said locking nut and rearwardly rotationaliyengageable with said front rod part through the intermediary of abiasing spring and means releasable on forward displacement of saidfront rod part relative to said housing, a feeding member rearwardlyclutchably engageable with said housing and with said feeding nut andforwardly rotationally engageable with said housing7 a biasing springurging said housing forward relative to said first rod part, and anexternal reference stop engageable by the front end of said housing.

Further features and objects of the invention will be apparent to Ithoseskilled in the art from the following detailed description, referencebeing made to the accompartying drawings, in which:

FILG. 1 is a diagrammatic illustration of one example of a brake riggingin which a slack adjuster according to the invention may be used,

`FiG. 2 shows, on a larger scale, one form of a slack adjuster accordingto the invention, in side view in the lower half of the figure, and inaxial section in the upper half of the ligure,

FIGS. 3-5 illustrate three different stages of a takeup operation of theslack adjuster of FIG. 2,

FlGS. 6-8 illustrate three different stages of a paying out operation ofthe slack `adjuster of FIG. 2, and

FG. 9 is a view similar to FIG. 2, but on a larger scale and onlyillustrating the part of the slack adjuster between the lines IX--IX inFIG. 2.

Referring first to FIG. l, 1 is a brake cylinder provided with a pistonrod 2 which lis pivotally connected to one end of a live brake lever 3,the other end of which is connected to a cross head 4 forming -a part ofa slack adjuster. The left hand or rear end of the slack adjuster is apart of a rod 5, the extreme left end of which is connected to a leversystem comprising a live brake lever 6 `and dead brake lever 7 forapplying blocks 8 against .a wheel 9. A dead brake lever 11i ispivotally connected .to a bracket on the brake cylinder 1 and isconnected to the live brake lever by a rod 11. The end of the dead brakelever 10 remote from the cylinder 1 is pivotally connected to a rod 12which is adapted to be connected to a lever system for applying thebrakes of another wheel. However, in order to simplify the followingexplanation, it will be assumed that the rod 12 is always kep-tstationary seeing that it.

is well known in the art that this makes no dilference as regards thefunction of the brake rigging or the slack adjuster. A rod `13 carryinga reference stop 14 is also pivotally connected Ito the said remote endof the dead brake lever 10. Thus, for the purposes of the followingexplanation, the reference stop 14 may be assumed to be stationary.

The brake rigging just described and shown in FIG. 1 is of conventionaltype. The slack adjuster according to the invention may of course beused in any other conventional type of brake rigging provided that therequired space is available.

Referring now particularly to FIGS. 2 4and 9, the slack yadjuster thereillustrated comprises an elongated housing 15 consisting of acylindrical shell closed at its front end by means of a front cover orplug 16, and at its rear end by means of a 4rear cover or plug 17. Afront rod part 1S extends into the housing 15 from the front endthereof, and a rear rod part 19 extends into the housing 15 from .therear end thereof. The front rod part -18 is rigidly connected to thecross head 4, FIG. 1, and is constructed in the form of a tube carryingat its rear end a collar member 20 to which a sleeve 21 is attached soasto extend rearwardly therefrom. The collar member Ztl' and the sleeve21 willY be referred -to inthe fol* lowing as the head of the frontrodpart 18. From this Apoint of view, the axial bore of the sleeve 21forms an enlarged portion of the `aida-l bore of the tubularv lfront' Yrod part 18.

The rear rod part 19 constitutes the front end illustrated in FG. 1 andis constructed in the form of a spindle having a steep screw thread,i.e., a screw thread Y er the ma The frontend of the rear rod part t9extends into the Y axialzbore of the head Zt, 2i and front rod part/t8and is slidablyguided Ytherein,"the clearance between theseparts shownin FIGS. 2-8 being merely illustrative, the rear rod part being moreoverentirely omitted in PEG. 9 to simplify the illustration. The rear rodpart 19 carries two nuts, viz., a front'nut 22 referred to in thefollowing as the locking nut, and a j rearfnut 23 referred to in thefollowing as the feedingnut.

Aballbearing 24 carried by the locking nut 22 is freely Y slidable inthe bore of Vthe Vcollar member 20. At its rear i i end, the locking nutZZis constructed with an inclined face 25 which Ais engageable with aninclinedv shoulder face Y 26iin Vthe interior of the bore of the sleeve2tlg lnthis"V Y manne applying the above definitions, theflocking nut 22Vis forwardly rotationally and rearwardly .clutchably engageable at aYclearance between faces provided in the inter'ior of the head 20, 21.

The feeding nut 23 basa Vfrontface which is frictionaily (thusclutchably) engageable with a rear face of the locking nut Z2. Thefeeding'nut is constructed with an outwardly projecting collar 27 at therear end thereof.

A coupling ring 2S isV slidably mounted on the feeding nut 23.adjacentthe'rear end thereof. The coupling ring' 28 is constructed atfits circumference with a rearwardly and inwardly inclined coupling face29. lntneneutral position of the slack adjuster, i.e., Ythe position inwhich no axialfor'ces are transmitted through the slack adjuster,YV thecoupling ring 281s located inside the bore of the head` .26), 21adjacent the rear end thereof.V The coupling ring 28 forms one race ofVa ball bearing,V the other lrace Vof which is denoted by thereferencecharacter Sil( A biasing compressional springV 3l isinserted between theball bearingracell and a fixed support 32' adjacent the front end.

of the feeding nut.V

' A feeding member in the form of a `sleeve 33 extends rearwardly fromthe feeding nut23 and is constructed at its front end with aninwardlyprojecting collar idrclarnped between the collar 27 of the feeding nut23 and the cou-.

pling ring 28 underthe influence of the biasing spring Si.. i

At its rear end, the feeding member 33 is'constructed with a radiallyoutwardly extending portion SS, which is'ccn-Y `structeclyatanrinclinedV rear face thereof withfa conical coupling face 36engageable with'a corresponding conical i face 37 provided Aon the,inner wall,l ofV the rear plug j' ofthe housing'of .the slack adjuster,thus constituting a-Q` clutchableengageruent between the feeding member33 t e n y n VVAball bearing 38 1s mounted-1n a fixed positionin the;housing at Vsonie distance in front of the by theportion 35 ofthefeeding member 33 in the neutral,

' position VVof the slack adjuster.

and the housing l5. Y

A plurality of balls 39 is'providediin inwardly/tapering radial holes ofthe, sleeve or. head portion -Elgin posiposition occupied'y Y tions suchas to engagev the coupling face 29 ofthe coupling ring 23 in the neutrallpositionof the slack adjuster.

Y vA sleevedtlV is slidably mounted inside the housing l5 and is urgedforwards against a shoulder face 4l under-the--in-f iuencel of laVbiasing spring` 42 interposed between fsaid' sleeve and a Xed abutment43 so that when not subjectedl to, forces in the rearward direction, thesleeve dil' will occupyra predetermined position within the housing.The. sleeve this `constructed with a cylindrical coupling face` member33 andthe.reaij end of the'` housing.- j

The `transmission :of theg lbraking .force will take the .gai-ortionqilt kin a osition 'jto beV engaged bylthey I Vcoupling facepofrtion cover ldof the housing t5.

scribed with particular reference to FIGS 'Z-.Sfof

scribed as follows:

During the braking stroke, "the ibraking force is transz. niittedthrough the slaclradjuster vvhich'thereby travels to ,the right in FIG.l, or in other `words travels in'thejdirec-V f tion delined above astheV forward direction. ,Ifjduring. i f this travel, the housing 1S ofthesrslaclr adjusterdesnot v l strilrethe reference stupid before acertain braking'fi'nrcezV hasy been developed, this is an indication`that theslack of -V the bralre-,riggingis too; small,andwpayaoutisftherefore- L required. lfon the other hand the housing l5doesstrilre v the reference stopxlt and is 'detainedthereby,and.the

front roddi thereafter continuesito travel beyondjacer Y.: tainpredetermined. distancebefore therfull brakingpres-f. Y sure isdevelopedtor Vis no trre'ached atj all)f-thisf=1is van in- A dicationthat the-'slack of thebrakeriggirng is,f toolgr eat andV take-up'isrequired. l

distance A from therefer'ence stop 1de When braking starts, thebrakin'gforce. maybe trans-fA il, mitted from the front rod partl tfo`the rear rod parti?? by two alternatiye ways, yviz., either'via thebiasingspringV dtthe housing the Y feeding memberSfthecoupling f ringVV2S, vthe ballV race. :35h/[liefbiasing.springt.3lY `amil z the feedingnut 23, or via the balls 39 V'directly to the icou-l plingjjring Zdandthen againvia the ball racetland thev biasing spring` S to the 'feeding,nut v'2,3 .whichfengagesq with thescrew thread` ofthejrearrod part.tandfis pre vented from rotating` relative thereto .by the;clutclnableiv i engagement between the ct'gllanZP/ 'of thefeeding nutZSand the colla'rlft .of the feeding memberg, andthe clutch f Yable,engagement Vbetweenvthe'portiong `of the feeding.

formerppath ifthebraking force-is lowerpthan the biasV i of the? spring4 6,whiledtwilltake the-latter path 'if thelj i brakingforce.isVhi-gher,than'thebiasofttiespring'46. I" 1 As regards .thelattertransmission path, it is v to l,be 4notedf-- that since the ballsV39 vengaigefwthfthe y-lindricalcou-f: pling face Vportionrld, FlG. Q,Qof thesleeve @they gare,E i' prevented from moving radiallyoutwardsand 'are thereby., Y forced lto transmit'"forward'axialL forces ffror'nlthe sleeve 21 (forming partfof'the head of thefrontlrQdpart 15 )Vt the coupling'faoe29,"FlG;j-9,of thecouplingzring 2S.; 1 Assumingl no wthat-the .brakingforcepinthe front' rod part t@ does not reachthevaluefof'the basofthespring A 3l before theright handqenlfof ythelhousingSi strikesfthefifi reference stopl 14, then allethe parts of the'slackadjiister i 1 will ,remainv in the' relativ'efpositions'illustrated in .'.FIG'S i I 2 vand'9` untilthis occurs, as illu'stratedin fFlG. 3 frorn' which it will be seen that thegcr'oss head thas'beenVrnoved'f` Y to theright through the distance A, bntno'relative movementof the parts of the slack adjuster hasftakenplace.

When the frontrodpart l'noyvjconftinues totravelio Y the right,therhousing .15' remains stationary;v -Y The clutchl Y i ing engagementbetween the yfaces 316;"and .37 'ifstherfefore' released, and owirigtoYtherrelativwe movementbetweenthe.`

`Coupling balls E? inthe ,neutral positionpf the-slachadjuSter, anoutwardlyandforwardlyainclined coupling fac'ejpo'rtion 25commencing'irnmediately inffrontof .the Zone 'ofgejn-Y gagernent ofthericonpling ,ballsY Vtvvitli, they cylindrical.

4dV in 'the ineutral position of the Vslack; adjuster. Y Y ,f

A'biasing compressioual spring f1.5 is :inserted between.Y 1 the frontfaceofthe collar?rnernlz-er'tlflforrningpartofv the head ofthe-front-rod part 1S) andtheffront-plugor head portion 21 and thesleeve do, the balls 39 arrive at the inclined surface portion 41 andare thereby released, with the result that the two nuts 22, 23 may nowbe displaced relative to the 4head portion 21 so as to establishengagement between the coupling faces and 26. By the engagement, thebraking force is now transmitted from the front rod part 1S to the rearrod part 19 via the locking nut 22, the latter being prevented fromrotating on the rear rod part by the clutchable (frictional) nature ofthe said engagement.

The result of the release of the coupling faces 36, 37 is that theindirect clutchable engagement of the feeding nut 23 With the housing 15through the feeding member 33 is interrupted so that the feeding nut 23now becomes free to rotate. At this juncture, however, no axial forcesact on the feeding nut 23, because its former axial coupling to thefront rod part 18 was released at the balls 39, so that it will notrotate, but will continue to move to the right along with the rear rodpart 19 on which it is carried, the latter being now axially coupled tothe front rod part 18 through the locking nut 22.

lf the continued .travel to the right of the assembly of the front rodpart 18, the locking nut 22, the rear rod part 19, the feeding nut 2-3and the feeding member 33, until the full braking pressure has beendeveloped, is not long enough to bring the portion 35 of the feedingmember 33 into engagement with the ball bearing 3S, no further changestake place, and when the braking force is released, all the occurrencesdescribed just take place in the reverse order. yIt is to be noted,however, that the yieldable mounting of the sleeve 4t) by means of thebiasing spring 42 and the shoulder 41 facilitates the reentering of theballs int-o the space between the cylindrical coupling faceV portion ofthe sleeve 40 and the inclined coupling face 29 of the coupling ring 2S.

The braking operation just described is a normal braking operationduring which no slack adjustment has taken place.

Suppose, however, that the travel of the front rod part 1S continuesthrough a certain distance P beyond the distance which the portion 35 ofthe feeding member 33 has to travel before engaging the ball bearing 38.When this occurs, the feeding nut 23 is detained by the said engagement,and since the rear rod portion 19 continues its travel to the rightowing to its axial coupling to the front rod part 18 via the locking nut22, the feeding nut 23 will rotate on the rear rod part 19 together withthe feeding member 33 and will thereby be screwed rearwards on the screwthread of the rear rod part 19. The relative positions which the partsoccupy on completion of the additional travel P is illustrated in FlG.4. From this ligure it will be seen that the total travel of the crosshead '-2- beyond the position illustrated in FIG. 3 is P-j-e-j-S, wheree is the distance between `the portion 35 of the feeding member 33 andthe ball bearing 3S is the neutral position of the slack adjuster, and Sis the axial clearance between the inclined shoulder .26 of the sleeve21 (front rod part 1S) and the inclined face 25 of the locking nut 22.It will also be seen that the locking nut 22 and the feeding nut 23 havenow been spaced apart at a mutual distance equal to P.

When the braking force is released, the restoring force of the brakerigging will pull the rear rod part 19 to the left, and this pull istransmitted to the front rod part 18 via the locking nut 22 and theinclined faces'25 and 26, the engagement ofthe latter preventing thelocking nut 22 from rotating on the rear rod part 19. The feeding nut 23is free to rotate but Will not do so because it is just idling and itwill'therefore follow the rearward movement of the rear rod part 19. Nochanges of the relative positions of the parts occur until the portion35 of the feeding member 33 is again engaged with the rear end of thehousing 15. y Thereby, the feeding nut 23 becomes again locked againstrotation, and as soon as the right hand end of the housing 15 has beendisengaged from the reference stop 14 and the restoring pull transmittedthrough the slack adjuster has decreased below the bias of the spring46, the #latter is capable of expanding, thereby displacing the housing15, th-e feeding member 33, the feeding nut 23 and the rear rod part 19as one solid entity to the right relative to the front rod part 18. Thelocking nut 22 will at first take part of this displacement, therebydisengaging the inclined faces 25 and 26, but as soon as it becomesaxially engaged with the front rod part 18 through the ball bearing 24,it will be prevented from taking further part of the said axialdisplacement and since it is now free to rotate, it will be screwedrelatively rearwards on the screw thread of the rear rod part 19 untilit engages the feeding nut 23.

On completion of the brake release stroke, the housing of the slackadjuster will again be in the position relative to the reference stop 14illustrated in FIG. 2. Towards the end of the relative movements justdescribed, the balls 39 will again be introduced between the couplingring 2S and the sleeve 40 in the same manner as described in connectionwith a normal braking operation.

The positions now occupied by the parts of the slack adjuster isillustrated in FIG. 5. It will be seen that all parts of the slack.adjuster are in exactly the safe positions as in FIG. 2, with theexception that the rear rod part 19 has been moved relatively forwardsthrough the distance P, meaning that the slack has been reduced by theamount P.

It will now be explained how the slack adjuster operates if the slack istoo small, e.g., owing to replacement of braking shoes. As previouslyexplained, the criterion of too small `slack is that the braking forcetransmitted through the slack adjuster increases 'beyond a certain valuealready before the housing .15 engages the reference stop 14. Supposethat this occurs when the front end of the housing 15 is still at adistance m from the reference stop 14 as illustrated in FIG. 6.

Up to this point the operation of the slack adju-ster has been the sameas in the case of nor-mal braking, the braking force Ihaving beentransmitted Via the direct path from the sleeve 21 (front rod part 18)Via the balls 39'the coupling ring 28, the ball race 3l), the biasingspring 31 and the feeding nut 23 to the rear rod part 19, seemg that inthis case t-he braking force is obviously greater than the bias of thespring 46.

Now, the bias of the spring 31 has lbeen selected equal to the saidcertain value at which the slack adjuster should react, and consequentlyin the position illustrated in FIG. 6, the spring 31 will yield. As soonas this occurs, the clamping engagement Iof the collar 34 of t-hefeeding member 33 between the coupling ring 28 and the collar 27 of thefeeding nut 23 is released, the feeding nut 23 following up the slightyielding movement of the coupling `ring 23 under the influence of thebiasing spring 46, so that no axial forces will occur between theflanges Stand 27, but these may in fact become slightly spaced apart.The `feeding member 33 consequently can no longer prevent the feedingnut 23 from rotating, and since the latter is subjected to an axialforce viz., the braking force, and since the locking nut 22 with which1t is in engagement is also free to rotate at the ball bearing 24, bothnuts 23 and 22 will start rotating, thereby being screwed forwards onthe screw thread of the rear rod part 19. This movement is followed upby the housing 15 under the influence of the biasing spring 46, Iwhichkeeps the housing in engagement with the coupling ring 28 via thefeeding member 33.

This state of things continues until the right hand end of the housing15 strikes the reference stop 14. When this occurs, the powertransmission path from the front rod part 1S to the coupling ring 28 viathe balls 39 is interrupted as previously described, because the balls39 become free to move radially outwards, and a power transmission pathis established from the front rod part '18 to the locking nut 22 via theinclined faces 257 26 instead,

whereby Vthe locking Vnut 22 Y Y is again prevented fromrotat;y Y ing. YThis position is illustrated in FIG. 7 andris in fact lthe' same as thatillustrated in FIG.Y 3. The slack adjustment has now been lcompleted andthebraking may bei continued until the fullbraking force hasbeendeveloped. During the development of the full braking force, theaxial distance between the portion V35 of 'cheV feeding v member 33 andVtheV ball bearing 38 will decrease but it will not be eliminated. YFIG, 8 illustrates the Iposition after the vbrakes have again beenreleased, and from a comparisonfof FEGS.

6 and 8 it will beseen that the amount of slack increase j Vthat wasestablishedduring the braking stroke is equal Y to the distance m inFG.V 6.

I claim:

1'. "An automatic slackadjuster foribrakegfcomprising an elongatedhousing, a frontrod apart extending into said housing from the front endthereof, arear rod part Vextending intorsaid housing from the rear endthereof and being constructed with a steep screw thread, a locking nutand a `feeding nut on said screw -thread,-said locking nut 4beingforwardlyrotationally engageable andrearwardly clutchably engageablewith said front rod part,v said feed-A l ing nut being forwardlyclutchably engageabletwith saidV locking nut and rearwardly rotationallyengageable with`V said front rod part, a coupling vmember slidablymounted on said 'feeding nut, a biasing spring urging said couplingmember rearwardly relative. -to said feeding nut, ballmeansengageablebetween said coupling member and said front rod part, meansfor releasing-said ballrneans from such engagement upon forwarddisplacement lofrsaidv front rod'part'relative to said housing, afeeding member rearwardly clutchably engageable with said housing andwith said feeding nut and forwardly rotationally engageable withV saidhousing, a biasing spring. urging said housing forwards relative to'said `lirst rodpart, and an external reference stop forwardlyengageable by said housing.

front rod part VKand said nuts in predetermined positions relativetosaid housing in axial engagement with one anf l otherin the neutralYposition of theslacl'` adjuster7 said front rod part and said frontnut` beingrlockedagainst mutual rotation and said twof nuts beingmutually none rotatableV when soV engaged, means Vfor'preventingrotation of said rear nut in the vneutral position thereof, butpermitting such rotationV on forwarddisplacenient of'saidf rear nutrelative to saidzhousing, coupling meansfor axialiy coupling said rearnutV to said yfront rod parts, saidV couplingmleans-being releasable'`on forwardmovementof 55 said front rod part relative tosaid housingfromits neutral nut for rotation upon increase of theaxialf forcetransmitted bysaid coupling means beyonda predetermined value, means foraxially coupling said frontnut to said front rod part on axialdisplacement of thelatter relative tosaid: housing from its neutralpositiongtherein, said'm'eans beingV constructed tolock'said front nutand said front rodpart against mutual rotation, stop means for limitingforward movement ofsaid rear nut'relativeto said housing-withoutpreventingrotation thereof, andan external reference sto for limitingforward movement oftsaid bruising;`

' position thereinV and being cons tructedto liberateV said rear.

constructed with a steep sc rewthread, a frontl nut and .agiV

rear nut carried by said screwV thread in engagement there-y with,biasing and stopgrmeans for keeping said front .rod part and `said nutsinl predetermined positions relative to Y Qin L, v s

saidhousing in vaxial engagement withione another inthe, Y'neutral'position of theslaci: adjuster, said fronty rod part t andY saidfront'ynutV being mutnallyrotatable,and;said tvio' Y nuts, being againstmutual 'rotation whenjlso ken-v zgaged,gm eans effectivein-the'neutralposition' ofsaid front, rod4 part for axiallyconpling'saidrear nutzrthereto,"alterfgV Y native Ymeans effective uponforward'displacementlof saidV Y front rod part relativetosaid'housingfor aXiallyfcouplin'g-gr said front nut thereto,g1 means, forinterconnectingthe vas`` sembly of said` nuts against relative rotationYinthe neutral.

position of the slacltadjuster; means for liberatingfthe asf sembly Vofsaid nuts' forV Vrotation onf increase of lthe :pull transmitted'by theVfront rod partywhile still inlits'neiitra'l g1 Y position, beyond. a*certain* value,a11d*forV stopping such` Y rotationl on dis'plaeement of'said; front rodjpart Vfrom its i Y neutralposition in saidhousing',meansl for-.'rotationaliy;V l detaining said rearnuton travelthereof.,beyond;aV certain-AV distance fromvrits neutral position, andanexternalrefer- Y f enceistop for limitingforward movementofsaid'ltiousing'.AV

e. An automatic slackjadj'usterfor.brakes'comprising-an Y elongatedhousing, a fronti,rodpart*extending'intosaid? housing from the frontlend thereof and constructetlwith anV enlarged head inside said housing,said` front" 'rod ,part

and head' ,being constructedwithian,axialborejnlhich'is'I enlarged intheZone ofsaid head,;`are`ar,rodparteigtehdingtinto V said housinglfro'rnf-the rear endl-'thereon saidrear', 'rodrpartihaving a steeplyscrewfthreaded portionV ea'rtendyA ing into the'bore of said front,rod-part, and Vhead?,vvitlrrout Y engaging therewith, a locking 'nut'andf'ak feeding vnut car-f-V riedby saidscrew!threadedfportioniinengagementt withV tliesCrew thr'ead'tnereof,said locking nut'beingjforwaidly j rotationally" and rearwardlylclntchably engageable atfa,` clearancebetween faces VVprovided inftbeinteriork of said" head adjacent the front endvr thereof, said vfeeding'nut being locatedto therear ofsaidV locking nut and beingforwardly :clutchablyV jengageable' therewith, said {feztetiing nut. Ybeingconstructed with an outwardlyrprojecting: collar at Y the rear endthereof, a'couplingl ring slidably mounted. 'on

said feeding nut adjacentthe rear endgthereof, said coupling ring being`constructed at'its'circumference'with aA rearwardly and inwardlyinclined coupling face, said coupling ring being located in theneutralpositionlofltheisla'ck l adjusterV inside said' Ibore' Vof' sai'djheadadjacent the .rear Y end thereof, a biasingV compressional springVbetweenffsaid.

wardly rotationallyengageable fat aV vclearance;between faces providedin the interior ofgsaid housing adjacent the rear endfthereof, aplurality ofcouplingl beinglpro- Vvided, Vinaini/ardlyK tapelingradial"holesfofsaid .headin 1. Y'

positions such asto engage saidfcoupliiigface ofsaidAcouplingfringuin'the neutrall Vposition'ofgthe sla'ckadjustenra couplingface being provided interorly. ofrs'aidhousing, saidjcoupling faceVvhaving` a Cylindrical coupling facejpo'r-A i v tion in a Vposition to,beengag'ed'by said2'coujcflingballsy i the neutral-position oftheslackadjustera'nd a'nz outwardly'f: t and forwardly inclined couplingface portion commencing ,innnediatelyV in front ofthe zone Vof engagennentfof;'saidf Y l coupling balls with saidcylindrical couplingface'fportion: in the neutral'position of thevslack adjuster, aibiasingcom-.V pressional spring in saidfhousingfbetvveen'saidhead and theVfrontVY endofsaid vhousing,*andzan eXternalireference-VV stop forlimiting yforwardmovement of said.h ousing'.V

No referenceslcited. Y

VY-nUANn A; andan, gnamma,V

ycoupling ring and a fixedC supportadjaent'fthe fronteendof said feedingnut, said biasingispringbeingrtatiohallysupa ported againstsaidfcouplingringa .feeding memberfeXf i vtending rearwardlyfromjsaidfeeding'nutand constructed Y at its. front endwith an Vinwardlyprojectingc ollarfclutch-v ably engageable rbetween said coupling ringand saidjo'utf` wardly projecting collar ofsraidpgfeelding'nut', saidgffeeding-Q member beingv constructed at itszfrearl endg-with varadially extending .portion which is rearwardly clutchablyandfor

1. AN AUTOMATIC SLACK ADJUSTER FOR BRAKES, COMPRISING AN ELONGATEDHOUSING, A FRONT ROD APART EXTENDING INTO SAID HOUSING FROM THE FRONTEND THEREOF, A REAR ROD PART EXTENDING INTO SAID HOUSING FROM THE REAREND THEREOF AND BEING CONSTRUCTED WITH A STEEP SCREW THREAD, A LOCKINGNUT AND A FEEDING NUT ON SAID SCREW THREAD, SAID LOCKING NUT BEINGFORWARDLY ROTATIONALLY ENGAGEABLE AND REARWARDLY CLUTCHABLY ENGAGEABLEWITH SAID FRONT ROD PART, SAID FEEDING NUT BEING FORWARLDY CLUTCHABLYENGAGEABLE WITH SAID LOCKING NUT AND REARWARDLY ROTATIONALLY ENGAGEABLEWITH SAID FRONT ROD PART, A COUPLING MEMBER SLIDABLY MOUNTED ON SAIDFEEDING NUT, A BIASING SPRING URGING SAID COUPLING MEMBER REARWARDLYRELATIVE TO SAID FEEDING NUT, BALL MEANS ENGAGEABLE BETWEEN SAIDCOUPLING MEMBER AND SAID FRONT ROD PART, MEANS FOR RELEASING SAID BALLMEANS FROM SUCH ENGAGEMENT UPON FORWARD DISPLACEMTN OF SAID FRONT RODPART RELATIVE TO SAID HOUSING, A FEEDING MEMBER REARWARDLY CLUTCHABLYENGAGEABLE WITH SAID HOUSING AND WITH SAID FEEDING NUT AND FORWARDLYROTATIONALLY ENGAGEABLE WITH SAID HOUSING, A BIASING SPRING URGING SAIDHOUSING FORWARDS RELATIVE TO SAID FIRST ROD PART, AND AN EXTERNALREFERENCE STOP FORWARDLY ENGAGEABLE BY SAID HOUSING.